<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="{{ url_for('static', filename='test.css')}}" >
</head>

<body>
{% block head %}
<div> This is head</div>
{% endblock %}

{% block content %}
<div> This is content</div>
{% endblock %}

{% block foot %}
<div> This is foot</div>
{% endblock %}

</body>
</html>